Jarrell Miller (right) returned an "adverse finding" in a drug-testing sample, casting doubt over his scheduled June 1 date with Anthony Joshua

KATIE Taylor’s unification fight with Delfine Persoon is in doubt after American heavyweight Jarrell ‘Big Baby’ Miller returned an "adverse finding" in a drug-testing sample.

It was only announced earlier this week that IBF/WBA/WBO champion Taylor champion would the Belgian on the undercard of Joshua-Miller, slated to take place at New York’s Madison Square Garden on June 1.

Taylor is a clear favourite to remain unbeaten in her 13th paid fight, with some of the bookies pricing her at 1/12 while Persoon is out at 6/1.

The June 1 fight is due to be Joshua’s American debut. However, both camps were informed that an adverse finding was detected in a random urine sample Miller gave to the Voluntary Anti-Doping Association (VADA) on March 20.

The Brooklyn heavyweight has tested positive for banned substance GW1516, a muscle growth enhancer which aids weight loss, according to reports.

Joshua, a 2012 Olympic champion like Taylor, has told promoter Eddie Hearn - who also promotes Taylor - that he’s prepared to fight a replacement.

"We are working with all relevant parties and will update with more details soon. AJ's preparation continues for June 1st at MSG," tweeted Hearn.

Miller's camp, Salita Promotions, also acknowledged the adverse finding on its Twitter account.

A statement read: "We are in the process of obtaining further information about VADA's finding and will have more to say soon on this developing situation.

"In the meantime Jarrell continues to train for his June 1 fight against Anthony Joshua."

The 30-year-old was kickboxing in 2014 when he tested positive for methylhexaneamine in a urine sample and was suspended for nine months by the California State Athletic Commission.

During their promotional tour for the fight, Miller revealed that both fighters had agreed to between 10 and 12 weeks of drug testing in the build-up to the bout.

Joshua, during the London leg of the tour, said: "I am on (drug testing scheme) ADAMS whereabouts, they have to know where I am for an hour every day and could walk in anytime.

"They can turn up any time during the day and that is a lifetime commitment. I have been on that since 2012 and I pay £40,000-a-fight to be tested by VADA two times a week."

Matchroom boss Hearn could now need to find a replacement fighter, with Kubrat Pulev, Luis Ortiz and Michael Hunter considered potential candidates.

Joshua retained his WBA, IBF, WBO and IBO titles when he stopped Alexander Povetkin in September.